Hubble Space Telescope — Expanding The Scientific Frontiers
Power of technology
Where the atmosphere doesn’t have far reaching effects. Above rain clouds and light pollution, that’s a perfect place for a telescope, bestowing an unobstructed view of the universe. — That’s where Hubble Space Telescope studies our universe. Hubble is the first major optical telescope to be placed in space. Scientists have used Hubble to observe the most distant stars and galaxies as well as the planets in our solar system. Orbiting about 340 miles above Earth, on a path inclined 28.5 degrees to the equator, at an average speed of 17,000 mph, and takes 95 minutes to complete one orbit. Its functions are powered by sunlight — has solar arrays that converts sunlight directly into electricity. Some part of the electricity is stored in its batteries so as to keep the telescope functioning while blocked from the direct rays of Sun.
Why the name Hubble?
Before jumping to the telescope, let’s understand why the name was chosen. Hubble Space Telescope is named after the famous astronomer Edwin Hubble. Hubble’s brilliant observation was that the red shift of galaxies was directly proportional to the distance of the galaxy from earth. That meant that things farther away from Earth were moving away faster. In other words, the universe must be expanding.
Why Hubble Space Telescope?
- You must be asking a question, “why a telescope in space?” “why not here on earth?”
— well, there’s a reason for that. Even the ground-based observatories are usually located in highly elevated areas to combat light pollution. But they still lack the precise image that scientists want to get as atmospheric turbulence limits the sharpness of images. (The effects of atmospheric turbulence are clear to anyone looking at the stars, this is why they appear to twinkle.) That’s the exact reason for placing the telescope in orbit. Moreover, the disadvantage of ground-based telescopes is that the Earth’s atmosphere absorbs much of the infrared and ultraviolet light that passes through it. Space telescopes can easily detect these waves.
Maintenance
Astronauts have serviced Hubble five times, on missions launched in 1993, 1997, 1999, 2002, and 2009.
Instruments Aboard Hubble Space Telescope
There has been a lot of transition in terms of scientific instruments onboard. Initial instruments on Hubble included the Wide Field Planetary Camera, the Goddard High Resolution Spectrograph (GHRS), Faint Object Camera (FOC), the Faint Object Spectrograph (FOS), and High Speed Photometer. Some of them have been replaced due to the upgradation of technology or have become obsolete. As of now, there are some of the instruments aboard Hubble that are relaying useful information to the scientists on earth. These have been discussed below.
The Hubble Space Telescope has three types of instruments that study the light coming from different regions of the universe. These include cameras, spectrographs, and interferometers.
For getting images of the universe, Hubble has two primary camera systems. These two are Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3). These camera systems are designed to provide wide-field imaging over a broad range of wavelengths.
Advanced Camera for Surveys (ACS)
ACS is an instrument that is used as the primary imaging instrument aboard HST. ACS was designed primarily for wide-field imagery in visible wavelengths, although it can also detect ultraviolet and near-infrared light as well. The observations undertaken with ACS provided astronomers with a view of the Universe with uniquely high sensitivity, as exemplified by the Hubble Ultra-Deep Field, and encompass a wide range of astronomical phenomena, from comets and planets in the Solar System to the most distant quasars known.
Spectrography
Any object that absorbs or emits light can be studied with a spectrograph to determine characteristics such as temperature, density, chemical composition and velocity. Presently, Hubble makes use of two such spectrographs — Space Telescope Imaging Spectrograph (STIS), and Cosmic Origins Spectrograph (COS). STIS serves as an all purpose spectrograph that precisely studies bright objects. COS studies faint levels of ultraviolent light emanating from distant cosmic sources, such as quasars in remote galaxies.
Cosmic Origins Spectrograph
The Cosmic Origins Spectrograph is an ultraviolet spectrograph that is optimized for high sensitivity and moderate spectral resolution of compact (point like) objects (stars, quasars, etc.). COS has two principal channels, one for Far Ultraviolet (FUV) spectroscopy covering 90–205 nm and one for Near Ultraviolet (NUV) spectroscopy spanning 170–320 nm.
Hubble’s interferometers serve a dual purpose — they help the telescope maintain a steady aim and also serve as a scientific instrument. The three interferometers aboard Hubble are called the Fine Guidance Sensors. The Fine Guidance Sensors measure the relative positions and brightnesses of stars.
FGS
Fine Guidance Sensors are very sensitive instruments. A fine guidance sensor (FGS) is an instrument on board a space telescope that provides high-precision pointing information as input to the telescope’s attitude control systems. The Hubble Space Telescope has three fine guidance sensors (FGSs). Two are used to point and lock the telescope onto the focused target, and the third can be used for position measurements — also known as astrometry. Because the FGSs are so accurate, they can be used to measure stellar distances and also to investigate binary star systems.
Space Telescope Imaging Spectrograph (STIS)
STIS is used to obtain high-resolution spectra of resolved objects and has the special ability to simultaneously obtain spectra from many different points along a target. Its working is similar to how a prism creates a rainbow — splits light into colours or wavelengths. Data is then used by scientists to study stars and other objects. STIS is proficient at locating black holes.
Wide Field Camera 3 (WFC3) — Wide Field Camera 3 is the main imager on the telescope. It has a camera that records visible as well as ultraviolet (UV) wavelengths of light and is 35 times more sensitive in the UV wavelengths than its predecessor, the Wide Field and Planetary Camera 2.
This powerful camera takes perfectly-clear pictures over a wide field of view and over a broad range of wavelengths.
Near Infrared Camera & Multi-Object Spectrometer (NICMOS)
A Second Generation Imager/Spectrograph is NICMOS. The only near-infrared (NIR) instrument on the HST is NICMOS. NICMOS has the ability to obtain images and spectroscopic observations of astronomical targets at near-infrared wavelengths. NICMOS must operate at a very low temperature to be sensitive in the NIR, necessitating the use of sophisticated cooling. Although NICMOS is currently inactive, most of its functionality is replaced by Hubble’s other science instruments.
Hubble Deep Field
It totally changed the perspective of astronomy. Concentrate your sight at a single point. Observe it. Study it. That’s what Hubble Deep Field is in layman’s terms.
Hubble Deep Field is the result of the power of concentrating on a single region in space. You might wish to study so and so star, just point the telescope. The Hubble Deep Field (HDF) is an image of a limited small region in the constellation Ursa Major. Its main function was to perform a series of observations by the Hubble Space Telescope. The area under inspection was about 2.6 arcminutes on a side, about one 24-millionth of the whole sky.
The image taken over ten consecutive days in the year 1995 was assembled from 342 separate exposures taken with the Space Telescope’s Wide Field and Planetary Camera 2.
Hubble avoids atmospheric airglow allowing it to take more sensitive visible and ultraviolet light images than can be obtained.
The field selected for the observations was selected after fulfilling several criteria. It’d to be at a high galactic latitude the reason being dust and obscuring matter in the plane of the Milky Way’s disc prevents observations of distant galaxies at low galactic latitudes. It’d to avoid the bright sources of visible light (such as foreground stars), infrared, ultraviolet, X-ray emissions, and more such criteria.
It was decided that the target should be in Hubble’s ‘continuous viewing zones’ (CVZs) — the areas of the sky which are not hidden by the Earth or the moon during Hubble’s orbit.
Hubble ultra Deep Field
The Hubble Ultra-Deep Field (HUDF) is a deep-field image of a small region of space in the constellation Fornax, containing an estimated 10,000 galaxies. It’s one of the most interesting pictures you’d ever see of the outer sky. It includes light from galaxies that existed about 13 billion years ago, some 400 to 800 million years after the Big Bang.
How does Hubble Communicate?
Hubble uses radio waves to send the pictures through the air back to Earth.
It’s an interesting process. Hubble has a communications system that enables the telescope to receive commands from Earth-bound controllers and to transmit large amounts of scientific and engineering data back to the ground.
Before sending commands to Hubble, first of all, it’s ensured what astronomical targets to observe. These targets have first to be identified by the Space Telescope Science Institute in Baltimore, Maryland. Then the identified target is sent to the Space Telescope Operations Control Center (STOCC) at NASA’s Goddard Space Flight Center in Greenbelt, Maryland — which operates and commands Hubble — uses NASA’s Space Network to communicate with Hubble. This network consists of a constellation of satellites in geosynchronous orbit named the Tracking and Data Relay Satellites (TDRS). Hubble commands are transmitted from the STOCC and routed through dedicated radio dishes at the White Sands Complex.
TDRS serves as a relay for commands and data going to and from Hubble. All of these transmissions are done in the S-band, a specific radio frequency range. The satellites send and receive signals through two different types of antennas, called multiple-access and single-access antennas.
Hubble transmits four main types of data: real-time science, real-time engineering, recorded science, and recorded engineering
Hubble’ Achievements
- Due to Hubble, we were able to determine that almost all the galaxies have black holes at their cores.
- Hubble helped the scientists to learn about the process of formation of the planets.
- It was only due to the observations of Hubble that scientists were able to determine the age of our universe — 13.7 billion years old.
- It observed a distant supernova that provides the evidence that universe began to speed up recently.
- Hubble discovered five moons around Pluto.
- In 2021: Observed a bizarre, 250-light-year-wide “superbubble” inside a nebula, spotted a galaxy with surprisingly little dark matter and saw a Jupiter-size exoplanet being born.
- It was Hubble Space Telescope that discovered organic molecule on a planet outside our solar system. The name of the planet is HD 189733b — is of the size of Jupiter. Molecule is methane — can perform chemocal reactions that are essential for life to thrive.
Difference between Hubble and James Webb Telescopes
There’s an advanced telescope that has been recently launched — James Webb Space Telescope. The difference between Hubble and Webb isn’t only in seeing back in time, but more than that — like clearer images, more description, and much more. Some of the differences have been mentioned below:
- In order to look deeper into space, Webb is designed to see the earliest stars and galaxies that formed in the Universe. For this, Webb has a much larger primary mirror in comparison to Hubble (2.7 times larger in diameter, or about 6 times larger in area), giving it more light-gathering power.
- The infrared instruments aboard have a longer wavelength coverage. In addition to this, they’ve improved sensitivity more than Hubble. It allows Webb to look further back in time than the Hubble. Infrared light is often very old light, due to a phenomenon called redshifting.
- Now coming to the distance between both the telescopes and earth. JWST will operate much farther from Earth, Webb telescope is about a million miles away, maintaining its extremely cold operating temperature, stable pointing, and higher observing efficiency. On the contrary, the Earth-orbiting Hubble, is in low-earth orbit, roughly 340 miles.
To know more about James Webb Space Telescope, click the link embedded below:
Hubble Space Telescope Last Days
None of the scientists can predict for long would Hubble be able to keep observing the universe. There were instances when the telescope couldn’t function properly, and these faults were dealt with.
Hubble went offline in 2021 for approximately a month after experiencing an issue with its main payload computer. The Hubble team fixed the problem by switching to backup hardware.
in October 2021, a problem was detected with the synchronization of Hubble’s internal messaging, sending all five of the observatory’s science instruments into a protective “safe mode.” The mission team managed to get all of the instruments back online over the next few months.
Our universe is on continuous move. Nothing remains stall here. Observing the light travelling long distances, Hubble functions similar to a time machine — it’s not today’s version of the distant objects we see — but the past. For example, when we look at the NGC 5728, a spiral galaxy which lies at a distance of around 130 million light-years from Earth, we see it as it was 130 million years ago. That’s the beauty of technology. Technologies like Hubble Space Telescope have so deeply entered our scientific bloodstream that we can’t think of evolving without them. When the time of Hubble will end, it’ll actually end with a vision. And fulfilling the vision scientists would place another advanced telescope in orbit. That’s how technological evolution works. That’s why James Webb Space Telescope has been honed to perfection. Hubble will be admired and would always remain a legend……..
